This application corresponds to Japanese Patent Application No. 11-344735 filed in JPO on Dec. 3, 1999, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an engine fuel injection control device wherein the fuel injection amount is controlled in accordance with the amount of air intake into the engine in order to prevent generation of smoke in the exhaust gas.
2. Description of the Related Art
Conventionally, in engine fuel injection control of, for example, diesel engines, smoke caused by incomplete combustion of the fuel is generated if the fuel injection is excessive with respect to the air intake amount of the engine, so in order to prevent production of such smoke, control has been proposed wherein the air intake amount actually provided into the engine is detected by disposing an air intake amount sensor in the air intake pipe, and the fuel injection amount is restricted such that the fuel injection amount is not excessive for the detected air intake amount (for example, Japanese Patent Application Laid-Open Publication Nos. 7-158483 and 8-303278).
With the fuel injection control of a diesel engine disclosed in Japanese Patent Application Laid-Open Publication No. 7-158483, a basic fuel injection amount calculated from the degree of accelerator opening and engine rotational speed is compared with a maximum fuel injection amount calculated from the intake amount of fresh air and the engine rotational speed, the smaller of the basic injection amount and maximum injection amount is taken as the final fuel injection amount. Moreover, if the basic fuel injection amount exceeds the maximum injection amount, the maximum fuel injection amount is increased in response to the difference (expressing the degree of cleanliness of the recirculated exhaust gas) between the ratios of the basic injection amount and the maximum fuel injection amount after and before the basic injection amount exceeds the maximum fuel injection amount, and the increased maximum fuel injection amount is taken as the final injection amount. Thereby, achievement of both prevention of generation of smoke during vehicle acceleration and smooth acceleration is aimed at.
With the diesel engine fuel injection control disclosed in Japanese Patent Application Laid-Open Publication No. 8-303278, a cylinder air intake amount found from a detected value of air intake amount is read. Moreover, a limit air excess amount is calculated by multiplying a limit air excess amount set with respect to the engine rotational speed by a limit air excess amount set with respect to the air intake pressure. By calculating an allowed maximum fuel injection amount based on these values, optimization of the diesel engine emissions and operating characteristics is aimed at.
However, since the distance between the air intake amount sensor and engine cylinders is the result of the addition not only of the length of the air intake pipe itself but also the length of the air intake manifold, there is usually an error, due to response lag, between the detected air intake amount detected by the air intake amount sensor and the amount of actual introduction of air into the cylinders. If the operating condition of the engine is a steady operating condition, such a response lag in regard to detection of air intake amount can be practically neglected in fuel injection amount control. However, a method in which more accurate calculation is carried out in order to perform more precise control has been studied. In this calculation, an air intake amount introduced into the cylinder is calculated more accurately by taking into account the response lag in respect of the detected air intake amount detected by the air intake amount sensor. Thereby, a smoke limit fuel injection amount regarded as a limit value for the generation of smoke is found from a calculated value of the air intake amount.
However, although such a calculation taking into account response lag functions normally when engine is in a steady operating condition, variability of response lag is produced when a condition shifts to a transient operating condition. When fuel injection is performed in accordance with the fuel injection amount found with respect to the air intake amount, problems can arise such as that smoke is generated, or the necessary engine output is not obtained because the fuel injection amount is excessively limited.
Accordingly, a problem to be solved lies in making it possible to determine a fuel injection amount such that smoke is not generated by detecting a shift of the engine to a transient operating condition and reliably ascertaining the air intake amount even when variability in the response lag occurs.
In view of the above, an object of the present invention is to provide an engine fuel injection control device. In this device, generation of smoke or insufficiency of engine output due to excessive limitation of the fuel injection amount can be prevented by detecting a shift of the engine to a transient operating condition and suitably determining the fuel injection amount for the air intake amount which is precisely determined, even if variability in the response lag occurs.
According to one aspect of the present invention, there is provided an engine fuel injection control device including basic fuel injection amount calculation means for calculating a basic fuel injection amount from engine rotational speed and amount of accelerator operation, and air intake amount detection means established in an air intake pipe of the engine for detecting the air intake amount provided to the engine. The engine fuel injection control device further includes inferred air intake amount calculation means for calculating an inferred air intake amount inferred to be provided to the engine by using the target fuel injection amount on an occasion prior to the current occasion and the rotational speed of the engine. The engine fuel injection control device still further includes final air intake amount determination means for comparing the air amount deviation between the detected air intake amount detected by the air intake amount detection means and the inferred air intake amount calculated by the inferred air intake amount calculation means with a predetermined value. This final air intake amount determination means determines the detected air intake amount as the final air intake amount in response to the air intake amount deviation being at or below the predetermined value. The final air intake amount determination means determines the inferred air intake amount as the final air intake amount in response to the air intake amount deviation being larger than the predetermined value. The engine fuel injection control device also includes smoke limit fuel injection amount calculation means for calculating a injectable smoke limit fuel injection amount at which smoke can be generated in relation to the final air intake amount determined by the final air intake amount determining means. The engine fuel injection control device also includes target fuel injection amount setting means for comparing the basic fuel injection amount calculated by the basic fuel injection amount calculating means with the smoke limit fuel injection amount and for setting the smaller of these values as the current target fuel injection amount.
With this engine fuel injection amount control device, an inferred air intake amount inferred air inferred to be provided to the engine is calculated by the inferred air intake amount calculation means, based on the target fuel injection amount on an occasion prior to the current occasion and the engine rotational speed. When the engine shifts to a transient state, whether the detected air intake amount detected by the air intake amount detection means is correct or not can be judged by comparison with the inferred air intake amount. If the air amount deviation between the detected air intake amount detected by the air intake amount detection means and the inferred air intake amount calculated by the inferred air intake amount calculation means is larger than a predetermined value, the operating condition of the engine may be deemed to be in a transient state. In this case, there is a response lag in the detected air intake amount detected by the air intake amount detection means compared with the air intake amount provided into the cylinder, so the final air intake amount determination means determines the inferred air intake amount which is closer to the actually provided air intake amount, as the final air intake amount.
The smoke limit fuel injection amount calculation means calculates an injectable smoke limit fuel injection amount in relation to the final air intake amount determined in this way. This is regarded as limit value of smoke occurrence. The target fuel injection amount setting means compares the basic fuel injection amount calculated by the basic fuel injection amount calculation means with the smoke limit fuel injection amount, and sets the smaller of these values as the current target fuel injection amount. Therefore, it is possible to perform fuel injection control which adjusts to the operating state and which prevents smoke occurrence.
The inferred air intake amount calculating means calculates the inferred air intake amount by correcting the basic inferred air intake amount determined from the target fuel injection amount on an occasion prior to the current occasion and from the engine rotational speed. This correction is carried out by using the injection amount deviation between the target fuel injection amount on the previous occasion and the target fuel injection amount on an occasion prior to the current occasion. The air intake amount varies with the time difference in accordance with the varying amount per unit time of the fuel injection amount. Consequently, it is possible to obtain a more accurate inferred air intake amount by performing a time lag correction based on the varying amount of the fuel injection amount in the calculation of the inferred value.
Preferably, the inferred air intake amount calculating means calculates the inferred air intake amount by using the following formula:
Mafe=Mafe(xe2x88x921)+Kxc3x97{Mafebxe2x88x92Mafe (xe2x88x921)}
where
Mafe is the current inferred air intake amount;
Mafe (xe2x88x921) is the inferred air intake amount on the previous occasion;
K is the lag correction coefficient calculated by using the injection amount deviation; and
Mafeb is the basic inferred air intake amount.
The lag correction coefficient K may be a value satisfying 0 less than K less than 1.
Preferably, the final air intake amount determining means calculates the air amount deviation by subtracting the inferred air intake amount from the detected air intake amount, compares the ratio calculated by dividing the absolute value of this air amount deviation by the inferred air intake amount with a prescribed error width, determines the detected air intake amount as the final air intake amount in response to the ratio being at or below the error width, and determines the inferred air intake amount as the final air intake amount in response to the ratio being larger than the error width.
Preferably, the final air intake amount determining means determines the inferred air intake amount as the final air intake amount only if the state of the ratio being larger than the error width continues for a prescribed time.
Preferably, the smoke limit fuel injection amount calculating means calculates the smoke limit fuel injection amount from a map which has been predetermined on the basis of the final air intake amount and the engine rotational speed.
Preferably, the engine fuel injection control device according to the present invention is applied to a common rail type diesel engine including a high-pressure supply pump, a common rail that accumulates fuel supplied from this high-pressure supply pump, an injector that injects fuel supplied from the common rail into an engine combustion chamber when an electromagnetic actuator is driven, and a controller that provides control current to the electromagnetic actuator for driving the electromagnetic actuator for a prescribed time in a prescribed period.
According to another aspect of the present invention, there is provided an engine fuel injection control device including a basic fuel injection amount calculation device for calculating a basic fuel injection amount from engine rotational speed and amount of accelerator operation, and an air intake amount detection device established in an air intake pipe of the engine for detecting the air intake amount provided to the engine. The engine fuel injection control device further includes an inferred air intake amount calculation device for calculating an inferred air intake amount inferred to be provided to the engine by using the target fuel injection amount on an occasion prior to the current occasion and the rotational speed of the engine. The engine fuel injection control device still further includes a final air intake amount determination device for comparing the air amount deviation between the detected air intake amount detected by the air intake amount detection device and the inferred air intake amount calculated by the inferred air intake amount calculation device with a predetermined value. This final air intake amount determination device determines the detected air intake amount as the final air intake amount in response to the air intake amount deviation being at or below the predetermined value. The final air intake amount determination device determines the inferred air intake amount as the final air intake amount in response to the air intake amount deviation being larger than the predetermined value. The engine fuel injection control device also includes a smoke limit fuel injection amount calculation device for calculating a injectable smoke limit fuel injection amount at which smoke can be generated in relation to the final air intake amount determined by the final air intake amount determining device. The engine fuel injection control device also includes a target fuel injection amount setting device for comparing the basic fuel injection amount calculated by the basic fuel injection amount calculating device with the smoke limit fuel injection amount and for setting the smaller of these values as the current target fuel injection amount.
Preferably the inferred air intake amount calculating device calculates the inferred air intake amount by correcting the basic inferred air intake amount determined from the target fuel injection amount on an occasion prior to the current occasion and from the engine rotational speed. This correction is performed, based on the injection amount deviation between the target fuel injection amount on the previous occasion and the target fuel injection amount on the occasion directly before the previous occasion.
Preferably the inferred air intake amount calculating device calculates the inferred air intake amount using the following formula:
Mafe=Mafe (xe2x88x921)+Kxc3x97{Mafebxe2x88x92Mafe (xe2x88x921)}
where
Mafe is the current inferred air intake amount;
Mafe (xe2x88x921) is the inferred air intake amount on the previous occasion;
K is the lag correction coefficient calculated using the injection amount deviation; and
Mafeb is the basic inferred air intake amount.
Preferably the lag correction coefficient K is a value satisfying 0 less than K less than 1.
Preferably, the final air intake amount determining device calculates the air amount deviation by subtracting the inferred air intake amount from the detected air intake amount, compares the ratio calculated by dividing the absolute value of this air amount deviation by the inferred air intake amount with a prescribed error width, determines the detected air intake amount as the final air intake amount in response to the ratio being at or below the error width, and determines the inferred air intake amount as the final air intake amount in response to the ratio being larger than the error width.
Preferably, the final air intake amount determining device determines the inferred air intake amount as the final air intake amount only if the state of the ratio being larger than the error width continues for a prescribed time.
According to another aspect of the present invention, there is provided an engine fuel injection control method including a basic fuel injection amount calculation step of calculating a basic fuel injection amount from engine rotational speed and amount of accelerator operation, and an air intake amount detection step of detecting the air intake amount provided to the engine. The engine fuel injection control method further includes an inferred air intake amount calculation step of calculating an inferred air intake amount inferred to be provided to the engine by using the target fuel injection amount on an occasion prior to the current occasion and the rotational speed of the engine. The engine fuel injection control method still further includes a final air intake amount determination step of comparing the air amount deviation between the detected air intake amount detected in the air intake amount detection step and the inferred air intake amount calculated in the inferred air intake amount calculation step with a predetermined value. In this final air intake amount determination step, the detected air intake amount is determined as the final air intake amount in response to the air intake amount deviation being at or below the predetermined value. In the final air intake amount determination step, the inferred air intake amount is determined as the final air intake amount in response to the air intake amount deviation being larger than the predetermined value. The engine fuel injection control method also includes a smoke limit fuel injection amount calculation step of calculating a injectable smoke limit fuel injection amount at which smoke can be generated in relation to the final air intake amount determined in the final air intake amount determining step. The engine fuel injection control method also includes a target fuel injection amount setting step of comparing the basic fuel injection amount calculated in the basic fuel injection amount calculating step with the smoke limit fuel injection amount and of setting the smaller of these values as the current target fuel injection amount.
Preferably, in the inferred air intake amount calculating step, the inferred air intake amount is calculated by correcting the basic inferred air intake amount determined from the target fuel injection amount on an occasion prior to the current occasion and from the engine rotational speed. This correction is performed, based on the injection amount deviation between the target fuel injection amount on the previous occasion and the target fuel injection amount on the occasion directly before the previous occasion.
Preferably, in the inferred air intake amount calculating step, the inferred air intake amount is calculated by using the following formula:
Mafe=Mafe (xe2x88x921)+Kxc3x97{Mafebxe2x88x92Mafe (xe2x88x921)}
where
Mafe is the current inferred air intake amount;
Mafe (xe2x88x921) is the inferred air intake amount on the previous occasion;
K is the lag correction coefficient calculated using the injection amount deviation; and
Mafeb is the basic inferred air intake amount.
Preferably the lag correction coefficient K is a value satisfying 0 less than K less than 1.
Preferably, in the final air intake amount determining step, the air amount deviation is calculated by subtracting the inferred air intake amount from the detected air intake amount, compares the ratio calculated by dividing the absolute value of this air amount deviation by the inferred air intake amount with a prescribed error width, determines the detected air intake amount as the final air intake amount in response to the ratio being at or below the error width, and determines the inferred air intake amount as the final air intake amount in response to the ratio being larger than the error width.
Preferably, in the final air intake amount determining step, the inferred air intake amount is determined as the final air intake amount only if the state of the ratio being larger than the error width continues for a prescribed time.